Art of producing centrifugal castings with a protective coating



Oct. 16, 1923.

w. D. MOORE ART OF PRODUCING CENTRIFUGAL CASTINGS WITH A PROTECTIVE COATING Filed March 8, 1923 11v VEN TOR VV/z 1 07/241 //00/?[ A TTORNEYJ Patented Oct. 16, 1923.

UNITED STATES PATENT OFFICE.

WILLIAM D. MOORE, OF BIRMINGHAM, ALABAMA, ASSIGNOR TO AMERICAN CAST IRON PIPE COMPANY, OF BIRMINGHAM, ALABAMA, A CORPORATION OF GEORGIA.

ART OF PRODUCING CENTRIFUGAL CASTINGS WITH A PROTECTIVE COATING.

Original application filed larch l, 1923, Serial No. 622,082. Divided and this application filed March 8, 1923. Serial No. 628,649.

I '0 all whom it may concern:

Be it known that I, WILLIAM D. Moons, a citizen of the United States, and resident of Birmingham, in the county of Jefferson and State of Alabama, have invented certain new and useful Improvements in the Art'of Producing Centrifugal Castin with a Protective Coating, of which the ollowing-is a specification.

This invention relates to the art of centrifugally casting hollow metal bodies such as pipe, and more particularly to the making of such bodies in centrifugall operated refractory molds; and has specia reference to the provision of metal castings having outer protective coatings produced in the casting operation and to the method of making such castings, this application being a division of my application Serial No. 622,- 082, filed March 1, 1923.

The principal objects of m present invention may be said to inclu e the provision of a casting, and more particularly a centrifugally produced metal casting such as ferrous pipe having a protective coating on its outer surface intimately united with the body of the casting for yielding a casting product which is capable of greatly resisting corrosive and other effects tending to shorten the life of the pipe; the further provision of a centrifugally produced casting having a protective coating which is readily produced during the casting operation in an efficacious and economical manner, and the provision of a method of producing the casting with the protective coating in a mold where the coating material is made to perform highly advantageous functions in the casting step for successfull permitting the centrifugal casting on re ractory and more particularly on green sand molds.

To the accomplishment of the foregoing and such other objects as may hereinafter appear, my invention consists in the elements and their relation one to the other, as hereinafter particularly described and sought to be defined in the claims, reference being had to the accompanying drawing showing a preferred embodiment of my invention, and in which:

Figure 1 is a cross-sectional view showing rotary mold after a casting operation and showing the facing on the surface of the casting functioning as a protective coating therefor.

Before describing my invention in detail, I will premise that in producing the centrifugally made casting with the protective coating, I first line a rotary mold with a refractory and more particularly a green or moist sand lining, which lining is then faced with a powdered substance having the properties of absorbing moisture from the lining and of taking a quick initial set to produce a tough membraneous coating or facin for the lining, and of being of a fusible c aracter so as to fuse to the outer surface of the casting to provide therefor the desired protective coating.

In lining the mold I first preferably provide a sand mixture having preferably a moisture content sufficient to provide a bonding power for the mixture to withstand the cutting and washing action of the iron and insufficient to produce that objectionable amount of steam generation which in practice has been found to result in pocketed or honeycomb defects in the casting. The sand mixture I prefer to employ contains 50% of silicia sand, 35% of sharp sand, and 15% of molding sand, this mixture containing from 7% to 11% of uncombined water calculated on the weight of the dry sand, all as described and claimed in my co-pending application Serial No. 623,650, filed March 8, 1923.

Referring now to Fi 1 of the drawings, I show diagrammatica ly a mold comprising a flask 10 provided with a plurality of perforations 11 distributed over the body thereof, these perforations defining vent holes for the es and steam generated during the castlng step, and this mold may be provided with a bell end 12 where pipe having a bell month end is desired to e produced. This flask is first lined with a refractory lining 13 which in the preferred practice of the invention comprises the moist sand mixture hereinbefore referred to.

As hereinbefore stated, it is a principal object of the present invention to produce centrifugally cast hollow bodies such as ferrous pipe having an outer protective coating which is readily produced during the casting operation, the protective coating roduced on the casting first forming a facmg for the refractor mold and having very desirable properties and functions as a facing for the refractor mold.

To accom lish these en s, I employ a facing materia which is applied to the surface of the moist sand mold in a powdered state, the powdered material having the properties ofabsorbing moisture from the sand lining 13, of taking a quick initial set to produce a tough membraneous or skin-like mold fac ing which is highly refractory, of having a low capacity for absorption of heat, of producing a mold wall impervious to the molten metal, and of being of a fusible'nature so as to readily unite with the skin of the casting to produce the desired protective coating therefor. I have discovered that such a facing is produced with the use of natural cement, this being a pulverized product resulting from the calcination of an argillaceous limestone at a temperature only suflicient to drive off the carbon dioxide.

The powdered natural cement may be ap-' action of the iron, which has the property of taking a quick initial set without any application of heat, and which upon setting expands with the result that the facing tends to pack itself or imbed itself into the sand mold proper and in the grains of the sand on the face of the mold so as to become at this stage of the process practically an integral part of the mold, the effect including "a conditiomng of the sand lining for the high resistance to destruction displayed thereby when molten metal is poured thereinto.

While in most instances I may employ natural cement in its natural state, in some instances it is desirable to mix with the natural cement a small percentage, say from 5% to 10% of an unctuous material such as graphite or talc, the purpose of this being to act as a lubricant to aid in the spreading of the cement on'the face of the mold.

The facing produced on the refractory lining possesses the property of being fused by the heat of the molten metal after the latter has been introduced into the mold and has distributed itself over the body thereof, the fusion of the cement to the metal caus ng the casting or pipe to retain a large portlon of the same on the finished casting as a protective coatin which displays great resistance to corroslon and which may be used to displace the ordinary tar or other coatings according to present practice. Fig. 2 of the drawings shows the refractory mold after a casting operation has taken place, and shows the hollow metal casting 16 provided with the outer coating 17 of the cementitious material. It is well known that cement inhibits corrosion in all iron products, and 1 have empirically demonstrated that the fused cement coatin on the outer surface of the casting materially contributes to its power of resistance to corrosion. It may be noted that because of the highly non-conducting character of the cement facing on the sand lining, that the sand is prevented from attaining sufiicient temperature during the casting operation to fuse withthe cement so that the cement coated pipe easily cleaves from the mold. Although I prefer to employ the moist sand lining mixture above lescribed with the natural cement facing for producing the coated casting, it will be understood that other sand lining mixtufes may be used to yield satisfactory resu ts.

The practice of my method andthe mak ing of protectively faced centrifugal castings will in the main be fully understood from the above detailed description thereof. Besides facilitating the casting procem, producing an efiicient mold and a coated metal product, I have found that with my method a cheap metal mixture may be employed, such for instance as a mixture having the elements phosphorus, carbon, silicon, manganese and sulphur reduced to low values and the costly silicon content reduced from about 1-}% down to about {$729, this being materially lower than the silicon content employed in metal mixtures with other processes. It will therefore be seen that the practice of my method is generally characterized by the ease of practicing the same, the emcient mold produced, the desired casting product obtained, and the inexpensive metal mixture used.

While I have disclosed the preferred form of my invention, it will be apparent that numerous changes may be made therein without departin from the spirit of the invention, defined 1n the following claims.

I claim:

1. In the; art of centrifugally casting metal bodies, the method of making a hollow metal casting with an outer protective coating fused to the body thereof, which consists in coating a refractory moist rotary mold with a powdered material having the property of absorbing moisture from the mold and of setting to form a fusible facing, and in pouring molten metal into the mold.

2. In the art of centrifugally casting metal bodies, the method of making a hollow metal casting with an outer protective coating united to the body which consists in coating the inner wall of a rotary refractory moist mold with a substance for forming a fusible facing, and in' pouring molten metal into the mold.

3. In the art of centrifugally casting metal bodies, the method of making a hollow metal casting with an outer protective coating united to the body which consists in coating the inner wall of a rotary refractory moist mold with a cem'entitious substance which sets to form a fusible facing, and in pouring molten metal into the mold.

4. In the art of casting metal bodies, a method of making a hollow metal casting with a protective coating which consists in coating a refractory moist mold with a powdered material having the property of absorbing moisture from the mold and setting to form a fusible facing, and in pouring molten metal into the mold.

5. In the art of casting metal bodies, a method of making a metal casting with a protectivecoatin which consists in coating a green sand mo d with a powered material having the roperty of absorbing moisture from the mo (1 and setting to-form a fusible facing, and in pouring molten metal into the mold.

6. In the art of casting metal bodies, a method of making a metal casting with a protective coating which consists in coating a refractory. moist mold with a powdered material having the property of absorbing moisture from the mold and setting to form a membraneous fusible facing, and in pour: ing molten metal into the mold.

In the art of casting metal bodies, a method of making a metal castingwith a protective coating which consists in coating a refractory unbaked mold with a cementitious substance having the property of taking a quick initial set to form a membraneous and fusible facing, and in pouring molten metal into the mold.

8. In the art of casting metal bodies, a method of making a metal casting with a protective coating which consists in coating a refractory unbaked mold with a powdered cementitious substance to form a fusible fac- .in ,,and in pouring molten metal into the cement to form a fusible facing and pouring molten metal into the mold.

10. In the art of casting metal b0dies,-a method of making a metal casting provided with a protective coating which consists in coating a refractory unbaked mold with a owdered natural cement to form a fusible acing and pouring molten metal into the mold.

11. In the art of casting metal bodies, a method of making a metal casting with a protective coating whichconsists in coating a refractory unbaked moldwith a powdered mixture of a cement and a lubricant to form a fusible facing on the surface of the mold and in pouring molten metal into the mold.

12. In the art of casting metal bodies, a method of making a metal casting with a protective coating which consists in coating a refractory unbaked mold with a mixture of natural cement and a lubricant to form a fusible facing on the surface of the mold and inpouring molten metal into the mold.

13. In the art of casting metal bodies, a method of making a metal casting with a protective coating which consists in coating a green sand mold having a moisture content of form 7% to 11% with powdered natural cement to form a fusible facing, and pouring molten metal into the mold.

14. In the art of casting metal bodies, the method ofmaking a metal casting with a protective coating which consists in coating a green sand mold having a moisture content of from 7% to 11%, with a substance having a property of absorbing moisture from the mold and setting to form a membraneous fusible coating.

15. In the art of casting metal bodies, a method of making a metal casting with a protective coatingwhich consists in coating a refractory unbaked mold with a mixture of natural cement and an unctuous material to form a skin-like fi s ible facing in the surface of the mold, and in pouring molten metal into the mold.

16. In the art of centrifugally casting ferrous metal pipe, a method of providing a protective coating for the pipe which consists in coating a. green sand mold with a powdered material having the properties of absorbing moisture from the mold and setting to form a fusible fa'ciiig, and in pouring molten ferrous metal iiito the mold.

17; A metal casting provided with a protective coating composed of natural cement.

18. A metal casting provided with a protective coating composed of natural cement and an unctuous material. 7

19, A metal pi provided with an outer protective coating composed of natural cement fused thereto,

20. A centrifugally cast pipeprovided on outer face with a protective coating fused to the body of the casting.

21. A centrifugally cast pipe provided on its outer face with a. protective cementitious coating fused to the body of the casting,

22. A centrifugally cast pipe provided on its outer face with a protective coating composed of a cement and an unotuous material fused to the body of the casting.

23. A metal casting provided with a protective coating composed of a substance obtained from the calcination of an argillaceous limestone.

24. A ferrous pipe casting composed of a metal mixture having a sillicon content of from 2 to 1 and provided with a protective coating on its outer surface composed of a substance obtained by the calcination of an argillaceous limestone.

25. A ferrous pipe casting composed of a metal mixture having a silicon content of from to 1 26. A centrifugally cast ferrous pipe composed of a metal mixture having a silicon content of from to 1 Signed at New York. city, in the county of New York and State of New York this 25 21st day of F eb., A. D. 1923.

WILLIAM D. MOORE. 

